The present invention relates to a differential case for motor vehicles.
DE 198 39 481 A1 describes a rear axle differential case for motor vehicles that comprises a pinion, which is driven with a cardan shaft or propeller shaft and which meshes with a crown wheel. The crown wheel in turn drives a differential gear, from which two output shafts extend out of the differential case on opposite sides. The crown wheel includes a ring gear and a ring gear holder, which is formed by the housing of the differential gear. The ring gear holder is arranged off-centered with respect to the differential gear. The ring gear of the crown wheel and the pinion are arranged on that side of the ring gear carrier that faces the xe2x80x9ccentral planexe2x80x9d of the differential gear. In this differential gear the pinion shaft is mounted with two double row tandem angular ball bearings, which are installed in an O arrangement. The first angular ball bearing is arranged directly at the pinion, and the second, at a distance from the pinion on the pinion shaft. Thus, the pinion is mounted in xe2x80x9coverhungxe2x80x9d position.
In most of the conventional motor vehicles with a rear axle drive, the propeller shaft runs in a xe2x80x9ccentral tunnelxe2x80x9d, that is essentially in the center of the motor vehicle from the transmission to the differential case towards the rear.
In some vehicles, such as an all wheel drive vehicle, described in EP 0901 423 B1, the propeller shaft runs laterally offset in relation to the central longitudinal plane of the motor vehicle. Correspondingly the differential case is also arranged off-centered at the rear axle. Owing to the off-centered arrangement of the differential case, two output shafts of different length are required at the rear axle, a feature that results in a more elaborate design and additional expense.
An object of the invention is to provide an improved differential case for motor vehicles with a laterally offset propeller shaft.
The problem is solved with the invention described and claimed hereinafter.
In an embodiment of the present invention, the ring gear of the crown wheel and the engaging pinion are arranged on that side of the ring gear carrier of the crown wheel that faces away from the differential gear of the differential case. In other words, the pinion and the ring gear of the crown wheel are arranged to be xe2x80x9creflectedxe2x80x9d, that is, on the xe2x80x9cother sidexe2x80x9d of the ring gear carrier of the crown wheel, as compared to a conventional differential gear.
A result of the xe2x80x9creflectedxe2x80x9d arrangement of the crown wheel ring gear and of the pinion is a number of significant design advantage. First of all, the reflected arrangement of the pinion and of the crown wheel ring gear allows the lateral offset of the propeller shaft to be compensated. Another advantage is that the pinion no longer has to be mounted in a xe2x80x9coverhungxe2x80x9d position, as is in DE 198 39 481 A1. In the prior art, the pinion head is virtually aligned with the differential case. In contrast, in the xe2x80x9creflectedxe2x80x9d arrangement, there is adequate space between the pinion head and the output shafts for a pinion bearing, a factor that is very advantageous to the rigidity of the pinion mounting.
According to a further development of the invention, the pinion shaft has two hollow cylindrical recesses, into each of which a pinion bearing is installed. One of the pinion bearings can be arranged directly xe2x80x9cbelowxe2x80x9d the pinion teeth, and the other pinion bearing xe2x80x9cjust behindxe2x80x9d the pinion teeth. This enables an extremely rigid pinion mounting, a feature that is advantageous for many reasons. A very rigid mounting increases, for example, the service life and the efficiency of the transmission. At the same time it reduces noise emissions.
Preferably angular ball bearings, installed in an O arrangement, are used for mounting the pinion. Thus, the bearing rigidity and the efficiency of the differential case can be further improved.
In various novel motor vehicle concepts, it is advantageous to use the central tunnel, which is the central longitudinal area of the motor vehicle, for housing various xe2x80x9cmotor vehicle componentsxe2x80x9d, such as the fuel tank. Such an arrangement is advantageous, especially with respect to xe2x80x9cderivabilityxe2x80x9d. Derivability means that one basic platform can be used for different model variants, for example limousine, station wagon, and coupe, with and without just slight reconstruction.
In such motor vehicles the propeller shaft runs laterally offset in relation to the central longitudinal axis of the motor vehicle by, for example, 200 mm. According to the invention, there is a gear or a chain drive to xe2x80x9cbridge the distancexe2x80x9d between the offset propeller shaft and the differential case pinion in the area of the rear axle. Thus, the differential case can still be arranged in the center of the motor vehicle, when the propeller shaft is offset relatively far. This feature has the significant advantage that two equally long or even identical output shafts can be used.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.